The present invention relates to a device for providing movement on an axis in at least one direction selected from the rotational direction and the x or y direction. More particularly, the invention relates to a device suitable for controlling the movement of a beam of light, such as from a laser, to generate two dimensional repeating patterns of light. In one embodiment, the invention is useful as a scanner for moving a small spot of light across bar codes in order to read them.
Scanners are devices which are used to control the movement of a beam of light, such as from a laser. The scanners are employed to aim optical elements such as mirrors, lenses and the like in order to reflect, collect and focus light. Scanners have found extensive application in the bar code industry. Bar codes consist of alternating light and dark bars which are used to present price or other information. One conventional method for reading them is to scan a focused beam of light in a line across the entire code. As light is absorbed and scattered by the bars, the resulting light modulation may be detected by a photodiode, for example, and processed by an electronic cash register or computer terminal.
In hand held bar code reading equipment compactness and simplicity of the scan mechanism are essential so the equipment can be portable. Single straight line scans are the simplest to generate and thus are often used in such equipment.
Orientation of the scanning beam with respect to the bar code is required however and this can slow down the reading process in either portable or fixed mount scanners. Various systems have therefore been devised to automatically scan a beam in multiple directions to overcome the need for tedious orientation.
U.S. Pat. No. 4,387,297 disclosed a portable scanning system in which a pair of motors and multiple drives are used to generate an omnidirectional pattern. Refinements of this device have not yet obviated the inherent clumsiness and size of the device due to the multiple drives and other equipment. Another beam scanning type device, shown in U.S. Pat. No. 4,639,070, uses an involved gear system for rotating various elements of the device. It also is quite complicated to manufacture.
U.S. Pat. No. 4,041,322 describes a device in which there is an angular displacement of a mirror in a single plane and at a constant speed. Several mirrors are used to provide the scanning signal at various angles.
U.S. Pat. No. 4,494,024, describes a spring activated motor, but it is a xe2x80x9cone shotxe2x80x9d spring driven motor in which heat is used to release torque by severing a chord. U.S. Pat. No. 3,631,274 describes a power supply in which a spring induces a voltage pulse in the coil.
U.S. Pat. No. 4,388,651 describes the faults of the prior art, stating that it is characterized generally by considerable complexity or by limited performance. This patent proposes to solve the problem using a single, small diameter rotating polygon mirror which is described as having increased scan efficiency by reflecting a beam from the polygon mirror facets two separate times. Examples of other systems are shown in U.S. Pat. No. 4,794,237, which employs a plurality of mirrors and a rotating disc, and in U.S. Pat. No. 4,795,224 which requires several motors and a relatively complicated prism ring which refracts light.
None of the prior art has yet been able to generate an appropriate optical pattern of lines to read bar codes at any orientation. Moreover, no prior art device has been found to produce omnidirectional scan patterns with a single optical element. Ideally, such a device would be small and very rapid, and could be held in one hand if constructed as a raster or omnidirectional device. It is desirable that the device be programmable to present one or more than one pattern of light with the fewest possible parts.
It is an object of this invention to provide a device for providing movement on an axis, such that a mirror can be attached to that axis, in order to impart combinations of rotational and x or y movement. Preferably the device imparts both movements, in order to generate a two dimensional scanning pattern produced by light reflected off on the mirror.
It is a particular object of the present invention to produce laser scan patterns which greatly reduce or eliminate the need for special orientation of either the bar code or the scanner in bar code reading equipment.
Yet another object is to provide a scanner which is programmable, and yet which is small and compact, and which operates at low power.
In it broadest form, the object of this invention is to provide a means for aiming or positioning an optical element in synchronization with electronic signals, which may be produced by oscillators, computers, music, voice, and the like, for information gathering or demonstration or entertainment purposes.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention have been accomplished in the manner described below. Specifically, the invention relates to a device for providing movement on an axis in at least one direction selected from the x or y direction and the rotational direction, and preferably in several directions, preferably simultaneously.
The device includes a shaft member having an axis defining a rotational direction about the axis of the shaft. A magnetic core means is mounted on the shaft and centers the shaft on the axis. The shaft itself may extend in one or both directions axially or may be the center of the core. The core generates a magnetic field in a plane which defines x and y coordinates with respect to the axis. Also included is a ferromagnetic ring surrounding the core and aligned in the plane described above. The ring has a coil means for receiving a varied electric current in the coil which is wrapped about the ring. The ring is positioned to provide a low reluctance path for the magnetic field and the magnetic field is aligned to penetrate only one side of the coil. Finally, means are provided for suspending the core with respect to the coil to permit relative movement therebetween in response to the varying frequency currents. Movement of the core causes movement on the shaft in at least the x-y direction or the rotational direction or combinations thereof.
In a preferred embodiment, the suspending means comprises at least one flat spring or elastic member which flexibly mounts the core with respect to the coil. The spring provides a restoring rotational torque to the core about the axis.
In another embodiment, the device is adapted to receive a first frequency that is a resonant frequency of the mounting means in the rotational direction. It is further adapted to receive a second frequency, a resonant frequency of the mounting means in the x-y direction. It is contemplated that the device would further include frequency mixer means for supplying various frequencies to the coil, and preferably at least the two resonant frequencies to the coil.
In yet another embodiment, a second coil is added. This coil is annularly positioned around the magnetic core and is located in the region of the magnetic field which defines the x and y coordinates. Preferably, the coil is wound around a bobbin device which locates the annular coil between the ring and the magnetic core. Means are provided for introducing electric current into the annular coil.
It is further contemplated that a mirror will be mounted on the axis, and the entire device can be incorporated into a scanner system as desired.
It is further contemplated that another kind of optical element such as a small semi conductor laser device may be directly mounted to the axis and mounted into a scanner system.
In one embodiment, the annular ferromagnetic ring includes a gap in its periphery at a location radially opposite the coil that is wound on the ring. In some instances, the coil may in fact comprise two coils, each of which is wound at a location spaced approximately 90xc2x0 radially from said gap. In that embodiment, the magnetic core element may be sized to have a length facing the gap and also facing that portion of the ring periphery which is 180xc2x0 radially from the gap. The core element width is shorter than the length because the two coils extend into the annular space. This generally rectangular shape increase the efficiency of the device.
Finally, in another embodiment, the ring may include a radially inwardly facing ferromagnetic screw which functions as a magnetic damper means. The screw is threaded in the ring to adjustably vary the distance between the radially inwardly facing end of the screw and the core element.